This invention relates to silicone compositions and a method for treating nonporous surfaces such as glass, porcelain, ceramic, polished or painted metal, plastic, and the like, to render them water, soil and stain repellent. Volatile organic compound (VOC) free cream, paste, powder and solid compositions are provided.
There has been extensive research and development involving silicone compositions for rendering nonporous surfaces water repellant. U.S. Pat. No. 2,612,458 (Stedman) discloses the application of substituted polysilicanes to windshields to achieve repellency. U.S. Pat. No. 2,923,653 (Stedman) discloses improved compositions employing alkoxy groups in the polysilicane to improve the repellency. U.S. Pat. No. 2,962,390 (Fain, et al.) describes a paste containing a solid rubbing agent and an alkyl alkoxy silane which when rubbed on a glass surface provides repellency. U.S. Pat. No. 3,244,541 (Fain, et al.) discloses acidic solutions of alkyl alkoxy silane monomers that produce rain repellent films on glass and which are also solvent resistant.
U.S. Pat. No. 3,579,540 (Ohlhausen) discloses water repellent film-forming compositions of alkylpolysiloxanes and acid or alkylpolysiloxanes, acid and solvent which result in durable and effective water repellent films on nonporous substrates. This patent also discloses the importance of adding the acid to the alcohol to form the intermediate half ester and then to add the alkylpolysiloxane in order to solublize the alkylpolysiloxane and eliminate the formation of two or three phases in the mixture. It also discloses that the alkylpolysiloxanes can be employed with solvents, diluents and extenders including colloidal pyrogenic silicas and clays. Isopropyl alcohol solvent was preferred. U.S. Pat. No. 3,817,769 (Fisher) discloses a rapid curing repellent composition by use of dyes, i.e., methylene blue, to give a durable and tough polysiloxane film. However, films prepared in accordance with Fisher""s examples gave poor repellency results unless sulfuric acid was also incorporated in the composition. U.S. Pat. No. 3,998,643 (Liddle), discloses the addition of hydrogen fluoride to the Ohlhausen compositions and processes with claimed improved repellency and durability.
U.S. Pat. No. 5,021,089 (Uwata, et al.), discloses a water repellent composition comprising a volatile organic solvent, a silyl phosphate and an organopolysiloxane, thus eliminating the mineral acid required in previously disclosed water repellent compositions. U.S. Pat. No. 5,417,744 (Gasmena) discloses a composition containing a fluorinated polysiloxane, a polysiloxane, a polyester modified polysiloxane, an acid, water and an alcohol to obtain an optically clear coating having hydrophobic properties. U.S. Pat. No. 5,584,917 (Kijima) discloses a water repellent composition comprising an amino group-containing polyorganosiloxane, an organic acid, a surfactant and an aqueous solvent. U.S. Pat. No. 5,697,991 (Frazer) discloses an alkypolysiloxane, mineral acid, solvent and a mild abrasive (0.5-3.0%, preferred 1%) as an improved water repellent treating compound wherein the abrasive serves to enhance dirt and grit removal. U.S. Pat. No. 5,759,618 (Taylor) discloses a strong phosphoric acid, hydrofluoric acid, sulfuric acid cleaning solution for glass surfaces prior to the application of an excess of an alkoxysilane/sulfuric acid solution to the glass surface with timing, temperature and humidity being critical for the removal of the excess in order to achieve an abrasive resistant, water repellent coating on the surface of the glass.
After almost three decades of research and development in water repellent silicone coatings, the dominant technology has involved the use of acidified solvent-based silicone compositions. A multitude of commercial products have been formulated and marketed utilizing some form of alkylsiloxane at about a 10% concentration and a mineral acid at about a 1% concentration and an alcoholic solvent. These alcoholic solutions all yield water repellent coatings on nonporous surfaces, particularly glass surfaces, by application directly onto the surface, usually by rubbing with a paper towel or cloth. Upon evaporation of the alcohol, a hazy film remains which is further polished with a dry wipe material to achieve the desired transparent water repellent coating. During the application process, the odor of the evaporating alcohol can be objectionable, particularly in the confined quarters of a shower or bathroom. OSHA recommends human exposure limits for most alcohols and other solvents to minimize health concerns, i.e., isopropanol (OSHA PEL: TWA 400 ppm, STEL 500 ppm) and ethanol (OSHA PEL: TWA 1000 ppm). These volatile solvents also contribute to air pollution and are considered to be undesirable volatile organic compounds (VOCs) by regulating authorities. These solvents have storage and handling limitations because they are also flammable and could ignite during application or form explosive mixtures if the vapors are confined.
Solvent-based silicone compositions currently have limited industrial application due to their flammability and the toxic vapor exposure to the workers. These solvent-based silicones require additional capital expenditures for explosion proof application equipment, exhaust equipment for vapor removal and scrubbing, and the monitoring of worker exposure to the solvent vapors.
The application of solvent-based silicone compositions utilizes excessive amounts of silicone per square foot of coverage provided due to the evaporation of the solvent and absorption of the silicone by the wipe material. Excessive amounts of the silicone remains in the wipe material and cannot be applied to the surface to be treated. The presence of solvents can also be incompatible with gaskets, paint, etc., associated with the surface being treated. Thus, a need exists for a water repellent composition that eliminates solvents and utilizes the silicone more effectively and economically.
The application of solvent-based silicone compositions also requires time for evaporation of the solvent and results in a hazy water repellent coating which is attributable to the separation of the acid, usually sulfuric acid, from the silicone on evaporation of the solvent. The resulting haze requires a second polishing step and/or dry wipe in order to achieve an optically clear coating. Thus, it is desirable to provide a composition that produces an optically clear water and soil repellent coating without excessive waiting, manpower or additional wiping.
The haze which develops upon application of a solvent based system to a nonporous surface and evaporation of the compatibilizing solvent results from the development of a silicone phase and a strong acid phase. This haze must then be wiped in order to intimately mix the silicone and acid phases onto the surface to remove the excess of the two phases and render it water and soil repellent.
Solvent-based silicone compositions also have storage temperature limitations. For example, alcoholic compositions in closed containers have been reported to xe2x80x9cexplodexe2x80x9d due to the high storage temperatures that can sometimes occur in warehouses or during transport in closed trucks and the like which results in an increase in the internal vapor pressure in the container leading to rupture. Not only does this cause a loss of product and packaging material but it presents a potential hazardous flammable and/or explosive event. There further exists a need for a water repellent silicone composition which is free of volatile organic compounds (VOCs), or VOC compliant, and which is nonhazardous.
Most solvent-based silicone compositions contain the active ingredients at about a 10%/wt level. Thus, almost 90% of the composition is solvent and this requires a large container in order to deliver the product to the customer. The larger container in turn requires more packaging material, larger boxes, more warehouse space, higher shipping costs and more shelf space. It would be very desirable to provide a concentrated silicone composition which has associated with it reduced manufacturing, packaging, storage, transportation and related sales costs, and which provides significantly greater coverage on the surface to the treated.
When dilute solvent-based silicone compositions are applied to a hard surface and wiped to a polished water repellent coating, the silicone coating is very thin, on the order of a mono molecular layer. These thin coatings will not hide the fine scratches and other defects in the hard surface that has been coated. It would also be desirable to provide a silicone coating composition which will leave an optically clear multimolecular layer which can hide or fill the fine scratches and other defects in the nonporous surface being coated and which results in a restored appearance to the surface.
In view of the above state of the art on research and development of silicone compositions, a number of improvements are needed.
This invention is directed to an essentially solventless water and soil repellent composition for treating nonporous surfaces. The composition consists essentially of a multi-phase dispersion of a silicone and an acid. A solid stabilizer is distributed in the multi-phase dispersion in an effective amount to stabilize the dispersion against separation. This essentially solventless silicone composition thereby overcomes the many disadvantages presently associated with solvent-based silicone compositions as set forth in the background of this invention.
The water and soil repellent compositions of this invention are useful for treatment of a variety of nonporous surfaces including glass, porcelain, ceramic, polished or painted (coated) metal, plastic, and the like, to render them water and soil repellent. The existing needs in the consumer, commercial and industrial fields are fulfilled by compositions of this invention because they are VOC free or VOC compliant, economical, non-flammable, practical, easy to apply, haze-free upon application, capable of homogeneous delivery of the active ingredients and offer improved water/soil repellency qualities.
In another embodiment, the water and soil repellent compositions of this invention are formulated and used in the physical form of a cream, paste or powder. In this embodiment, an additive may be used, as described hereinafter, to dilute the silicone and/or the acid phase of the composition. However, in any of these physical forms, the solid stabilizer compatibilizes the phases against separation. These forms of the silicone compositions enable multi-molecular and transparent coatings to be formed on a variety of nonporous surfaces. Furthermore, these multi-layered coatings hide or fill fine scratches and other defects in the nonporous surface being coated. Thus, the compositions and methods of this invention enable the restoration of nonporous surfaces, such as glass, which develop fine scratches and other defects in use.
Methods of preparing the water and soil repellent compositions are also provided by this invention. In the solventless compositions, silicone compounds and neat acid (without solvent) are mixed with a solid stabilizer in an effective amount to compatibilize or couple the components in a homogeneous mixture. In some cases, it may be desirable to heat the mixture and/or employ high-shear mixing to achieve the desired intimate blending of the components to ensure stabilization. The resulting composition of silicone fluid, acid and stabilizer, may be a cream, paste, powder or solid, depending upon the most desired form for the intended application. It has been found that a solid stabilizer is most advantageously employed in the form of fine particles. The fine particles enable the intimate delivery of the silicone and acid in the proper proportion to the surface to be treated. The solid stabilizer is contained in an amount from about 5 to about 85 percent by weight of the composition depending on the product type desired, and preferably consists of particles having an average size of less than about 100 microns, more preferably about 5 to about 50 microns, and having a specific gravity on the order of about 0.12 to 2.9 gm/cc, more preferably for creams and pastes about 0.12 to about 1.8 gm/cc. A wide variety of silicones, acids and solid stabilizers may be utilized in accordance with the principles of this invention as understood with respect to the following detailed description.
In accordance with the above summary, the objectives of this invention are to provide methods for rendering nonporous surfaces demonstrably water, soil and stain repellent with compositions of matter that are (1) non-flammable, VOC free or VOC compliant and essentially solventless, (2) more easily applied as a cream, paste or powder, (3) optically clear films, which may be multi-molecular to fill in microscopic surface scratches, (4) storage stable, (5) provide greater coverage per weight or volume applied, and (6) which are more durable and more resistant to removal by soaps, solvents, detergents and abrasives. These objectives are accomplished by stabilizing a multi-phase dispersion of a silicone and an acid against separation to form a stabilized cream, paste or powder by the use of a solid stabilizer distributed in the dispersion in an effective amount.
In accordance with a best mode of this invention, improved water and soil repellent, nonflammable, VOC free compositions for nonporous surfaces are prepared by mixing an organosilicone compound with an acid and an effective amount of a solid stabilizer in the absence of a volatile organic compound.
A. Silicones
Generally, the silicone fluids can be described by the formula (A): 
in which
n is an integer from 1 to about 1000,
R(1) and R(2) are independently lower alkyl, substituted alkyl, alkenyl, halogenated alkyl, alkoxy, or halogenated alkoxy radicals containing from 1 to 8 carbon atoms; aryl, halogenated aryl, phenoxy, alkylphenoxy, halogenated phenoxy or halogenated alkylphenoxy radicals containing about 6 to 14 carbon atoms; hydrogen, hydroxy, or halogen; and combinations thereof, and
R(3) and R(4) are independently alkyl, substituted alkyl, alkenyl, halogenated alkyl, phenyl, alkylphenyl, substituted phenyl, hydroxyl, halogen, hydrogen or alkoxy, phenoxy, substituted alkoxy, substituted phenoxy, halogenated phenoxy, halogenated alkylphenoxy, and combinations thereof.
Suitable organosilicone compounds include silicone fluids such as polydialkylpolysiloxanes, polyalkylpolyalkoxypolysiloxanes, polyalkylhydrogensiloxanes, polyalkylarylpolysiloxanes, organofunctional polysiloxanes, fluorosubstituted alkylpolysiloxanes, cyclic siloxanes, and the like having terminal trialkylsiloxy, dialkylarylsiloxy, dialkylsilanol, and other organofunctional groups, and the like, and combinations thereof. Suitable cyclic siloxanes are hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane and decamethylcyclopentasiloxane. Copolymer fluids such as polyalkylhydrodimethylsiloxanes are also suitable. The fluids need not be linear but may also be branched. These silicone fluids of various molecular weights are commercially available as described and are listed in the literature of silicone fluid suppliers such as Wacker Silicones Corporation, Adrian, Mich.; Gelest, Inc., Tullytown, Pa.; Petrarch Systems, Bristol, Pa.; General Electric Co., Waterford, N.Y.; Osi Specialties, Inc. (Witco Corporation), Danbury, Conn.; Genesee Polymers Corp., Midland, Mich.; Dow Coming Corp., Midland, Mich.; Allied Signal, Inc., Performance Chemicals Div., Morristown, N.J.; PCR, Inc., Gainsville, Fla.; etc.
The relative amounts of components will vary to achieve the objectives of this invention and, in general, the amounts, in percent by weight, are about 20 to about 85 silicone, about 2 to about 20 acid and about 8 to about 85 solid stabilizer. As set forth in the examples which follow for creams, the ranges (percent by weight) are about 57-83 silicone, about 7.4-15.3 acid and about 5.5-34.3 solid stabilizer. Pastes and semi-solids range (percent by weight) from about 33.6-80.5 silicone, about 2-12.5 acid and about 9-62.8 solid stabilizer. For powders, the silicone may be reduced, for example, to lower amounts of about 20 percent by weight with a higher amount of stabilizer, i.e., about 75 percent by weight and about 2-3 percent by weight of acid. However, the following examples illustrate and do not limit the scope of the invention.
B. Acids
Suitable acids which are encompassed by the present invention are both mineral acids and their acidic salts along with strong organic acids. Included are sulfuric acid, sulfurous acid, hydrofluoric acid, hydrochloric acid, hydrobromic acid, phosphoric acid, phosphorous acid, pyrophosphoric acid, nitric acid, hydrogen sulfide, iodic acid, periodic acid, chromic acid, sulfamic acid, fluorosilicic acid, chlorosulfonic acid, fluorosulfonic acid, ammonium bifluoride, sodium bisulfate, mono- di- and trichloroacetic acid, mono- di- and trifluoroacetic acid, p-toluene sulfonic acid, benzene sulfonic acid, ethylsulfonic acid, methylsulfonic acid, ethylenedisulfonic acid, dodecylsulfonic acid, trifluoromethylsulfonic acid, perfluoroalkylcarboxylic acids, oleum, perfluoroalkylsulfonic acids, maleic acid, picric acid, trihydroxybenzoic acid, trinitrophenol and mixtures thereof.
In certain selected applications the acid component of the composition may be generated in situ by employing acid generating substances such as chlorosilanes, phosphorous trichloride, phosphorous tribromide, aluminum chloride, sulfonylchloride, acid chlorides, and the like, in the compositions of this invention. These materials react with the water which is adsorbed on the surface to be treated. This reaction generates (in situ) the strong acid required for the proper bonding of the silicone to the surface treated.
C. Solid Stabilizers
Solid stabilizers that have been found suitable for use in combination with the silicones and acids of the water and soil repellent compositions of this invention include mica, hydrocarbon waxes, polyethylene, polypropylene, polytetrafluoroethylene, phenolic resins, polyvinylchloride, crystalline graphite, amorphous graphite, carbon black, silicas, boron nitride, carnauba wax, glass microspheres, ceramic microspheres, perlite, vermiculite, talc and combinations thereof. It is desirable to have the solid stabilizers in a finely divided state to achieve the intimate delivery of the silicone and the acid in the proper proportion to the surface and to achieve the desired form of the composition for a particular end use application.
Particularly suitable solid stabilizers are those with particle sizes less than 100 microns, preferably in the 5-50 micron range, and having a specific gravity of about 0.12 to about 2.9 gm/cc, more preferably for creams and pastes about 0.12 to about 1.8 gm/cc in order to achieve good shelf life. The finer the particle size the less critical the specific gravity becomes.
Solid stabilizers must not be basic or reactive with acids. Such solids as powdered metals, metal oxides, metal carbonates, metal hydroxides, metallic soaps such as zinc stearate, amines, polyamino resins, and the like, would neutralize the acids in the compositions of this invention and deteriorate or prevent the bonding of the silicones to the surface to be treated.
On occasion, when making a cream, paste, powder or solid, it is desirable to admix the compositions of this invention with liquid or solid additives, including water, glycols, and the like, in order to achieve the desired performance of the composition, i.e., in order to achieve the desired coating thickness of the water and soil resistant coating on certain surfaces. In these cases, the additives will increase the silicone and/or the acid phases of the multi-phase dispersion, but the solid stabilizer will still be effective in the composition. However, in order to achieve the advantages of a VOC free or solventless form of the compositions of this invention, solvents are essentially excluded. For example, in order to maintain the desirable features of being xe2x80x9cVOC-freexe2x80x9d, the additives must meet Part 59 of the National Volatile Organic Compound Emission Standards for Consumer and Commercial Products; Section 59203 Standards for Consumer Products, Subpart (f) requirements:
(1) Has a vapor pressure of less than 0.1 millimeters of mercury at 20 degrees Celsius; or
(2) Consists of more than 12 carbon atoms, if the vapor pressure is unknown; or
(3) Has a melting point higher than 20 degrees Celsius and does not sublime (i.e., does not change directly from a solid into a gas without melting), if the vapor pressure is unknown.
or, they must have been excluded from the definition of xe2x80x9cVolatile Organic Compoundxe2x80x9d such as various halogenated organic compounds; certain classes of perfluorocarbons; cyclic, branched, or linear completely methylated siloxanes; waxes; or low-reactive organic compounds that have been exempted by the United States Environmental Protection Agency.
Additionally, for use in the compositions of this invention, these additives cannot interact with the silicone fluids, acids or the solid stabilizers employed in the compositions of this invention or with the effective application of the compositions to the surface to be treated. Examples of additives which meet all the criterion would be perchloroethylene, parachlorobenzotrifluoride (Oxsol 100, supplied by Occidental Chemical Corporation), decamethylcyclo-pentasiloxane, diethyleneglycol dibutylether (vapor pressure less than 0.01 mm Hg at 20 degrees Celsius), linear alkylbenzene sulfonate, glycerylmonostearate, stearic acid, hydrocarbon waxes, and the like.
Ancillary additives such as fragrances or colorants may also be added to the compositions of this invention to enhance the features of the compositions for various markets.
The principles of this invention and its parameters will be further understood with reference to the following detailed examples, procedures and discussion which serve to illustrate the types of materials and processes which can be utilized in practicing this invention. These examples and procedures are considered to be exemplary of this invention, and should not be considered as limiting in view of the broad disclosure of the principles of this invention.
1. Application of Water and Soil Repellent Silicone Compositions to Nonporous Surfaces
Glass mirrors (12xe2x80x3xc3x9712xe2x80x3) were employed in the general testing program and are cleaned with an abrasive cleanser, i.e., xe2x80x9cMiracle Scrubxe2x80x9d, an excellent, multi-surface, hard surface abrasive cleaner supplied by Unelko Corporation of Scottsdale, Ariz., to remove all surface residues including prior water and soil repellent compositions. The cleanser is removed from the cleaned surface by flushing with water. If the surface is properly cleaned, the rinse water will form a continuous smooth coating of water across the cleaned surface of the glass. The mirrors are then placed in a vertical position to drain and then dried with paper towels. The cleaned mirror surface is then allowed to equilibrate with the atmosphere for 24 hours prior to the application and evaluation of the water and soil repellent compositions.
Other nonporous surfaces such as porcelain, ceramic tiles, chrome, stainless steel, plastics and the like may also be employed in the evaluation of water and soil repellent compositions.
Application of the silicone compositions to the horizontal, cleaned mirror surface may be accomplished in various ways. With the currently available alcoholic silicone compositions, it is generally recommended by the suppliers to apply an excess of the liquid to the surface to be treated and then spread the liquid over the surface with an applicator such as a paper towel or cloth in order to cover the entire surface with the solution. The solvent is then allowed to evaporate which results in a hazy surface. The haze is then polished until the surface is clear with a dry applicator.
With the compositions of this invention it has been found that only a small amount of the composition need be applied to the mirror surface or to the applicator since the effective coverage has been found to be about 1000 sq feet per ounce of material, i.e., 30 milligrams/sq foot. Currently available solvent-based silicone compositions are claimed by suppliers to cover about 25 sq feet per ounce of material.
Applicators that have been found to be adequate for the compositions of this invention include paper towels, cloths, sponges, foamed plastics and the like. Acid resistant applicators are preferred for repeated applications of the acidic compositions. The compositions are wiped onto the mirror surface until clear, and a smooth homogeneous coating is achieved. This is basically a one step process as there is no waiting for solvent evaporation and no residual haze which has to be removed in a second wiping of the surface as occurs with the application of solvent based compositions. The coated mirror surfaces are then ready for testing of repellency and durability.
2. Evaluation of Coating for Water Repellency and Durability
a. Water Drop Test: Several drops of water are applied in a line across the mirror surface with the surface in a horizontal position. The contact angle of the drops are observed and the repellency ranked as
b. Drop Mobility Test: The mirror is then slowly raised on the end that parallels the line of the drops placed on the treated surface. The angle of the mirror or the height of the raised edged of the mirror from the flat supporting surface at which time the drops begin to flow down the inclined mirror is observed. The smaller the angle or the height of the edge, the better the repellency and contact angle. The following ranking is employed:
c. Spray and Blow Test: A spray bottle fitted with an adjustable sprayer set to deliver a spray or fine stream of water is employed in this test. The coated mirror is again placed in a horizontal position and 4 to 5 pumps of water spray/stream are delivered to the surface of the mirror test specimen with the stream in a slightly raised position from horizontal. The spray droplets are then observed over the area sprayed. The droplets are varied in size and are ranked in the same matter as the Water Drop Test above with the additional observation as to the abundance of the smaller drop sizes.
After the spray pattern of drops are evaluated the blow test is conducted. The ease with which the drops will flow in the direction of the air blow and the degree of blow hardness is noted:
d. Marker Repellency and Detergent Durability Test: A paper towel dipped in a strong basic detergent solution, i.e., a 50% aqueous solution of xe2x80x9cEasy Greenxe2x80x9d, a heavy grease and stain cleaner composition supplied by Unelko Corporation, Scottsdale, Ariz., is rubbed vigorously on half of the coated surface of the mirror. The excess detergent is removed from the surface with a water rinse and hand wash to assure that all the detergent has been removed. The mirror is then dried with a paper towel. To determine the degree of residual repellency a black xe2x80x9cMagic Markerxe2x80x9d, i.e., as supplied by Dennison Stationary Products Co., Framingham, Mass., is stroked across the unwashed coated surface and then across the washed coated surface and the streak observed. On an xe2x80x9cExcellentxe2x80x9d water repellent and soil repellent coating the marker will leave only a trail of fine droplets and a streak which is hardly visible. For a xe2x80x9cGoodxe2x80x9d evaluation the streak will have slightly larger drops but no streaks. For a xe2x80x9cFairxe2x80x9d evaluation the drops will again be larger but the streak may have light solid streaks of black. And, for a xe2x80x9cPoorxe2x80x9d evaluation the streak will be essentially solid with perhaps a few large drop areas. Most coatings based on the compositions and methods of this invention have both xe2x80x9cExcellentxe2x80x9d Marker Repellency and xe2x80x9cExcellentxe2x80x9d Detergent Durability ratings.
It has also been observed that the mirror coatings resulting from the application of the compositions of this invention generally result in a mirror surface that is brighter in appearance and one that also appears to have been restored as noted by the disappearance of minor scratches from the surface of the glass. It is believed that this is due to a multimolecular complex coating being deposited on the glass surface by the compositions of this invention. Thin monomolecular coatings are thought to be deposited from solvent systems which do not result in restorative features to the glass surface.